BSOD while playing games like WOW and LoL now just random crashes

[ERBZ1r]

i recently bought this desktop off of ebay everything worked fine for like a week.
at first i would get BSOD only while playing games like league of legends, sometimes it'd happen every 10 mins others it wouldnt happen all day. and it usually would say something like IRQL not less or equal there were quite a few tho and the BS wouldnt stay up but more then 2seconds so kinda hard to get all it said.
but now my compputer is just straight up freezing and i dont even get BS. it just freezes and stays there unable to do anything.

heres system info:

OS Name Microsoft Windows 7 Professional
Version 6.1.7601 Service Pack 1 Build 7601
Other OS Description Not Available
OS Manufacturer Microsoft Corporation
System Name USER-PC
System Manufacturer BIOSTAR Group
System Model TF7150U-M7
System Type X86-based PC
Processor Intel(R) Core(TM)2 Quad CPU Q9400 @ 2.66GHz, 2664 Mhz, 4 Core(s), 4 Logical Processor(s)
BIOS Version/Date Phoenix Technologies, LTD 6.00 PG, 8/28/2008
SMBIOS Version 2.5
Windows Directory C:\Windows
System Directory C:\Windows\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "6.1.7601.17514"
User Name user-PC\user
Time Zone Pacific Daylight Time
Installed Physical Memory (RAM) 4.00 GB
Total Physical Memory 3.00 GB
Available Physical Memory 2.16 GB
Total Virtual Memory 6.00 GB
Available Virtual Memory 5.14 GB
Page File Space 3.00 GB
Page File C:\pagefile.sys

need anything else just lemme know. thanks a bunch [:

 

[fseal]

If it was shipped to you, first thing I would do is open it up and make sure all the parts are properly seated. All kinds of things could have come loose during shipment. Video card could be sideways in it's slot. Ram chips partially unseated. The heatsink may have even poped off partially and your CPU could be overheating and locking up.

It happens quite often on computers that get shipped around...

 

[ERBZ1r]

yea ive done that already everything seems to be in place.. I purchased a new CPU fan with heat sink a few weeks ago and thats all setup properly, i have real temp and its consistently at 41 - 39 - 41 - 39 C's. there's a heat sink below that tho i think its the northbridge or something like that, says biostar on it and that gets pretty hot. idk how to deal with that tho. if thats even the problem.